Women ages 40 to 49 do not need routine breast cancer screening with mammography, according to a Canadian preventive care task force.

Action Points

Explain that new guidelines from the Canadian Task Force on Preventive Health Care recommend against screening mammography in the 40 to 49 age group for women at average risk of breast cancer.

Note further that these guidelines recommend mammography only every 2 to 3 years for women at average risk ages 50 to 74 and recommend against using MRI, routine breast clinical examination, and breast self-examination for breast cancer screening.

Women ages 40 to 49 do not need routine breast cancer screening with mammography, according to a Canadian preventive care task force.

Breast cancer screening for women of average risk in that age group results in a "relatively small" mortality benefit, which may be countered by an increased risk of overdiagnosis and unnecessary treatment.

In the final analysis, however, the decision to undergo screening mammography should remain with the individual patient and treating physician, who should thoroughly discuss the tradeoff between benefits and harms, as well as patient preferences, the guideline authors wrote in an article published online in CMAJ.

"We have recommended a screening interval of every two to three years for women 50 to 74 years of age using available evidence from randomized, controlled trials," Marcello Tonelli, MD, of the University of Alberta in Edmonton, and co-authors from the Canadian Task Force on Preventive Care wrote in conclusion.

"The concept of individualizing the interval for screening with mammography based on breast density or other risk factors is appealing but requires further study."

"Finally, given the importance of patient preferences for appropriate decision-making, further studies are needed to determine the best way to communicate information about the potential benefits and harms of mammography."

Citing evidence of overdiagnosis and unnecessary testing and treatment resulting from mammographic screening, Peter C. Gotzsche, MD, of the Nordic Cochrane Center in Copenhagen, wrote, "If screening had been a drug, it would have been withdrawn from the market."

The Canadian guidelines add another log to the opinion fires that have flared off and on since the U.S. Preventive Services Task Force (USPSTF) made similar recommendations in 2009. Debate over the need for screening mammography in women ages 40 to 49 continued through 2010, with multiple individuals and organizations taking sides.

The debate has shown no signs of losing steam. At various times during 2011, MedPage Today has reported studies showing that mammographic screening in women 40 to 49 offers a worthwhile mortality benefit and others that have found only a trivial benefit.

Last summer, the American College of Obstetricians and Gynecologists came out in support of mammographic screening beginning at age 40.

The Canadian task force found no evidence to support screening before age 50 for women at average risk. Members of the task force made the decision after updating and evaluating the systematic review the USPSTF performed before recommending age 50 for the start of routine mammographic screening.

The analysis showed that 2,108 women ages 40 to 49 would have to be screened every two to three years to prevent one breast cancer death. Screening that younger age group would lead to 690 false-positive mammography results and 75 unnecessary breast biopsies, the task force members wrote.

In contrast, the number needed to screen (NNS) dropped to 721 for women ages 50 to 69. Those women would incur 204 false-positives and 26 unnecessary biopsies.

Among women ages 70 to 74, mammography had an NNS of 451, false-positive results in 96 cases, and 11 unnecessary biopsies.

The task force made no recommendation regarding mammographic screening in women 75 and older, citing a lack of data to guide decision making.

Consistent with its U.S. counterpart, the Canadian task force recommended against routine use of MRI for breast cancer screening and against routine clinical breast examinations, and recommended that clinicians not advise women to perform breast self-examination on a routine basis.

Authors of the guidelines emphasized that the recommendations apply only to women with an average risk of breast cancer.

In the editorial, Gotzsche lauded the guidelines as "an important step in the right direction, away from the prevailing attitude that a women who does not undergo screening is irresponsible."

He cited the following recent studies suggesting "that it may be most wise to avoid screening altogether, at any age":

A Danish study showed that women ages 55 to 74 who had regular mammography had a 1% annual decrease in breast cancer mortality, as compared with a 2% decrease each year in an unscreened population (BMJ 2010; 340: c1241)

A study covering much of Europe that showed a 37% decline in breast cancer mortality from 1989 to 2005 that began before many of the countries had organized screening programs (BMJ 2010; 340: c4480, c3620)

An analysis of six European countries that introduced breast cancer screening 10 to 15 years apart and showed no relationship between the start of screening and breast cancer mortality. In fact, all of the countries had similar breast cancer mortality (BMJ 2011; 343: d4411)

"The best method we have to reduce the risk of breast cancer is to stop the screening program," Gotzsche wrote. "This could reduce the risk by one-third in the screened age group, as the level of overdiagnosis in countries with organized screening programs is about 50%."

Accessibility Statement

At MedPage Today, we are committed to ensuring that individuals with disabilities can access all of the content offered by MedPage Today through our website and other properties. If you are having trouble accessing www.medpagetoday.com, MedPageToday's mobile apps, please email legal@ziffdavis.com for assistance. Please put "ADA Inquiry" in the subject line of your email.